Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of an array of autoantibodies, including antibodies to DNA, antibodies to nuclear antigens and antibodies to ribonucleoproteins. The progression of the disease is associated with general clinical manifestations and damage to tissues and organs caused by deposition of immune complexes. Similar to other autoimmune conditions, the etiology of SLE is multifactorial entailing genetic, environmental, hormonal and immunological factors. No specific treatment aimed towards the prevention or cure of SLE is available.
The human monoclonal anti-DNA antibody termed 16/6Id bears a common idiotype (Shoenfeld et al., 1983). The idiotype was found to have clinical relevance in SLE patients. Thus, the 16/6Id was found to be expressed on anti-DNA antibodies of 54% of SLE patients with active disease (Isenberg et al., 1984) and in affected organs of patients with SLE (Isenberg and Collins, 1985). Mice of inbred strains that do not develop any spontaneous autoimmune diseases were immunized with this human anti-DNA 16/6Id mAb and developed the major hallmarks of SLE in humans and in the spontaneous murine models for this disease (Mendlovic et al., 1988). Thus, following immunization, the mice produced antibodies specific to the 16/6Id, antibodies that bear the 16/6Id and antibodies directed against different nuclear antigens (dsDNA, ssDNA, Sm, ribonucleoprotein, Ro, La and others). The serological findings were associated with leukopenia, elevated erythrocyte sedimentation rate, proteinuria, abundance of immune complexes in the kidneys and sclerosis of the glomeruli (Mendlovic et al., 1988), which are typical manifestations of SLE.
A murine anti-16/6Id mAb (Ab2) derived from mice with experimental SLE was also capable of inducing the experimental disease in mice (Mendlovic et al., 1989) similar to the 16/6Id (Ab1). Moreover, a murine anti-DNA mAb that expresses the 16/6Id was prepared from mice afflicted with experimental SLE. The antibody Ab3 termed 5G12 reacted with antibodies specific to the 16/6Id. Immunization with the latter antibody resulted in the induction of experimental SLE with similar manifestations as observed following immunization with the human 16/6Id (Ab1) and with the murine anti-16/6Id (Ab2) mAbs (Waisman et al., 1993). These results show the importance of the 16/6Id network in the induction and progression of SLE in mice.
In order to understand the mechanism by which self-antibodies associated with SLE arise, the present inventor has produced a variety of monoclonal autoantibodies derived from C3H.SW mice in which experimental SLE was induced. As a rule, the monoclonal autoantibodies that were capable of eliciting antibodies that bear the 16/6Id or react with it were found to be pathogenic and thus capable of inducing experimental SLE in mice (Fricke et al., 1990; Sthoeger et al., 1993).
Later on, the variable (V) regions of nine autoantibodies that bind either DNA or HeLa nuclear extract (NE), isolated from the C3H.SW mice with experimental SLE, were sequenced (Waisman and Mozes, 1993). Monoclonal antibodies with different specificity were analyzed in an attempt to determine the connections between the different autoantibodies. Three mAb were found to bind DNA, and were shown to exhibit sequence characteristics of pathogenic anti-DNA antibodies. One of these mAb, designated 2C4C2, was shown to use a heavy (H) chain V region gene (VH) identical to the VH of anti-DNA mAb isolated from other lupus-prone mice, namely (NZB×NZW)F1. The light (L) chain V region gene (VL) of mAb 2C4C2 is 98% homologous to the VL of another anti-DNA mAb, also isolated from (NZB×NZW)F1 mice. The other two anti-DNA mAb, designated 5G12-4 and 5G12-6, share 93% of their VH sequences with that of mAb 2C4C2. Based on the analysis of these mAbs, it appeared that autoantibodies found in mice with experimental SLE use genetic elements similar to those used by mAb that were isolated from mouse strains which develop lupus spontaneously.
T cells play an important role in the induction and development of experimental SLE. Thus, T cell lines and clones specific to the 16/6Id were shown to induce experimental SLE in syngeneic recipients similarly to the 16/6Id antibody. Therefore, following the inoculation of the activated cells of the lines, the mice developed both the serology and the renal damage which is typical to SLE (Fricke et al., 1991).
As described above, the mAb 5G12 that was isolated from mice with experimental SLE and was shown to bind DNA and bear the 16/6Id, is capable of inducing experimental SLE in mice (Waisman et al., 1993). T cells that react specifically to mAb by proliferation, are probably reacting to peptides representing sequences from their complementarity-determining regions (CDR). It is very likely that the T cells recognize the V regions of the above antibodies since they do not react with other antibodies that carry the same constant region but have different specificities. Within the variable region, the regions with the highest probability to be recognized are the CDR, since those are the regions that differ the most between the various antibodies. The CDR regions of the VH sequences of the nine pathogenic murine mAb mentioned above that induce SLE in mice, are boxed in FIG. 1 of Waisman and Mozes, 1993, in which the complete nucleotide and deduced amino acid sequences for the variable heavy chains (VH) of the nine mAbs are presented.
International PCT Patent Publication No. WO 96/30057 of the present applicants describes peptides based on the CDR regions of pathogenic mAbs isolated from mice with experimental SLE, in particular peptides Ia to IIIa, based on the CDR1, CDR2 and CDR3 regions, respectively, of the VH chain of the murine mAb termed 5G12, and peptides IVa and Va, based on the CDR1 and CDR3 regions, respectively, of the VH chain of the murine mAb termed 2C4C2. These peptides have the sequences substantially as denoted by SEQ ID NO:1 to SEQ ID NO: 5 as follows:
TGYYMQWVKQSPEKSLEWIG(Ia)[SEQ ID NO: 1] EINPSTGGTTYNQKFKAKAT(IIa)[SEQ ID NO: 2] YYCARFLWEPYAMDYWGQGS(IIIa)[SEQ ID NO: 3] GYNMNWVKQSHGKSLEWIG(IVa)[SEQ ID NO: 4] YYCARSGRYGNYWGQTL(Va)[SEQ ID NO: 5]
These peptides and, in particular, the peptides Ia and IIIa, herein designated mCDR1 [SEQ ID NO:1] and mCDR3 [SEQ ID NO:3], respectively, were shown by the inventor to be capable, when administered in PBS, of inhibiting T cell priming to either the appropriate mCDR peptide or to the whole anti-DNA 16/6Id mAb of either murine or human origin (Waisman et al., 1997). The peptides mCDR1 and mCDR3 were further shown by the inventor to either prevent or treat an already established SLE that is either induced by the human anti-DNA 16/6Id mAb or that develops spontaneously in the SLE prone mice (NZB×NZW) F1 or MRL/lpr/lpr (Eilat et al., 2000 and 2001).